The present invention relates to the art of mass spectroscopy, and in particular, to a method and system for high sensitivity, rapid, high efficiency mass spectroscopy.
It is known in the field of mass spectroscopy to provide spectrometers with an elongated conductor having multipole conductors which act as ion transmitters. In PCT Publication WO 99/38185 (the contents of which is incorporated herein by reference), a method and apparatus are disclosed for providing ion transmission between an ion source and a spectrometer. The ion transmission device includes a multipole rod set and a damping gas which dampens spatial and energy spreads of ions generated by a pulsed ion source. The multipole rod set has the effect of guiding the ions along an ion path so that they can be directed to the inlet of a mass spectrometer.
The WO '185 publication discloses a MALDI (matrix-assisted laser desorption/ionization) ion source for producing a small jet of matrix and analyte molecules and ions and which have a wide range of energy spreads. The ion transmission device of WO '185 spreads out the generated ions along the multipole ion guide axis to provide a quasi-continuous beam while i) reducing the energy spread of ions emitted from the source and ii) at least partially suppressing unwanted fragmented analyte ions. These ions are delivered to a time-of-flight spectrometer or other spectrometers.
The apparatus described in WO '185 provides that single multiple rod sets or two or more rod sets can be used. Regardless of the number of rod sets used or the number of rods provided therein, the conductors merely provide ion guidance and possible energy damping by way of collision with a damping gas within the ion guide itself. No provision is made to enhance the efficiency or improve the speed of movement while retaining integrity of the ion beam sent to a mass spectrometer.
Another disclosure, U.S. Pat. No. 6,111,250 to Thomson, et al., discloses a mass spectrometer which includes rod sets constructed to create an axial field, e.g., a DC axial field. The Thomson, et al. '250 disclosure provides for speeding the passage of ions through an ion guide and causing the ions to be fragmented. The ion source is disclosed as being an electrospray or ion spray device such as those described in U.S. Pat. Nos. 4,935,624 and 4,861,988, or a corona discharge needle or a plasma, as shown in U.S. Pat. No. 4,861,965. The ions are directed and their speed controlled for introduction into a “time-of-flight” mass analyzer. In one embodiment, Thomson, et al. disclose the use of a set of auxiliary rods in combination with a set of quadrupole rods for the purpose of, among other things, introducing very low energy ions into a quadrupole mass analyzer. There is no disclosure by Thomson, et al. regarding transmitting intact analyte ions as a substantially continuous ion beam for highly sensitive, rapid mass analysis.
While there are numerous disclosures relating to the art of mass spectroscopy of analyte ions, there is an ever increasing demand for high speed and accurate mass spectroscopy of specimens, especially dilute specimens having only trace amounts of analyte ions. It is the purpose of the present invention to meet this and other needs in the art of mass spectroscopy.